The present application is based on Japanese Patent Application No. 2002-289614, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a chained type large current fusible link unit with fuse circuit structures each containing terminal parts with fusible members connected thereto, which are linked in a chain manner through the fusible members.
2. Related Art
JP-A-2000-133114 discloses conventional fusible link unit for example. One of fusible link units of this type as shown in FIGS. 14 through 16 is known. The fusible link unit designated by reference numeral 100, as shown in FIG. 14, is generally composed of first and second fuse circuit structures 101 and 102 and a housing 103 into which those fuse circuit structures 101 and 102 are assembled.
The first fuse circuit structure 101, as illustrated in FIG. 15, is made up of a linking plate 104, a plurality of terminal parts 106a and 106b, which are coupled through fusible members 105 to the linking plate 104, a battery terminal 107 extended from one end of the linking plate 104, and a common terminal part 108 coupled through a fusible member 105a to the other end of the linking plate 104. The first fuse circuit structure 101 is formed by pressing a conductive flat plate member (not shown).
The second fuse circuit structure 102, as shown in FIG. 16, is made up of a linking plate 109, a plurality of terminal parts 111a and 111b, which are coupled through fusible members 110 to the linking plate 109, and a common terminal part 112 extended from the other end of the linking plate 109. The first fuse circuit structure 101 is formed by pressing a conductive flat plate member (not shown).
As shown in FIG. 14, the housing 103 is shaped like a rectangular parallelepiped, and contains a circuit-structure accommodating chamber 114 with an opening 113 open to the upper. The housing further includes a plurality of connector housing portions 115 and a plurality of terminal supports 116, which are located under the circuit-structure accommodating chamber 114.
As shown in FIG. 14, the first and second fuse circuit structures 101 and 102 are each inserted into the circuit-structure accommodating chamber 114, through the opening 113 of the housing 103. In this case, an extending direction of the flat surface of each fuse circuit structure is an insertion direction, and the terminal parts (106a, 106b, 111a, 111b) of the fuse circuit structure are first inserted as an insertion tip part.
When the first and second fuse circuit structures 101 and 102 are completely inserted into the circuit-structure accommodating chamber, the linking plates 104 and 109 of those fuse circuit structures 101 and 102 are located within the circuit-structure accommodating chamber 114. The terminal parts 106a, 106b, 111a, and 111b are set at predetermined positions of the connector housing portions 115 and the terminal supports 116.
Next, the common terminal parts 108 and 112 of the first and second fuse circuit structures 101 and 102 are fastened together to the housing 103 by means of a bolt 117. The first and second fuse circuit structures 101 and 102 are electrically connected to each other to thereby form a desired fuse circuit.
The battery terminal 107 is also fastened to the housing 103 by means of a bolt 117b. A terminal of a battery cable (not shown) is connected to the battery terminal 107. Connected to the terminal parts 106a and 111a in the connector housing portions 115 are the terminals of the counter connectors 118. LA terminals 119 are connected to the terminal parts 106b and 111b of the terminal supports 116 by means of screws. The connectors of the counter connector 118 and the LA terminals 119 are connected to loads by way of cables 120. Power source is distributed from a battery to those loads, through a fuse circuit. When shortcircuiting occurs in any of the loads and overcurrent flows into the related fusible member 105 (110), the fuse member burns out by heating to thereby prevent trouble by overcurrent.
In the fusible link unit 100 thus constructed, the first and second fuse circuit structures 101 and 102, shaped like flat plates, are assembled into the housing 103 to thereby form a unit. Therefore, a fuse circuit containing a number of fusible members (fuses) 105 and 110 may be made considerably compact. In particular, as shown in FIG. 14, the first and second fuse circuit structures 101 and 102 may be disposed in a state that those structures are merely spaced a narrow distance W apart from each other. Accordingly, to the fuse circuit extension, what a designer has to do is to slightly increase the housing 103 in the width direction Y, not in the longitudinal direction L.
In the conventional fusible link unit, the first and second fuse circuit structures 101 and 102 are each formed with one flat plate member. Accordingly, current flows always through the linking plates 104 and 109 even if it is fed from any of the terminal parts 106a, 111a, 106b, and 111b. Accordingly, a problem arises that temperature of the linking plates 104 and 109 rises by the current flowing therethrough.
To lessen the temperature rise, all one has to do is to increase the areas of the linking plates 104 and 109. However, to make the housing 103 compact, it is desirable to minimize the external dimensions of the first and second fuse circuit structures 101 and 102. Accordingly, it is preferable to avoid increasing the external dimensions of the first and second fuse circuit structures 101 and 102.
Accordingly, an object of the present invention is to provide a fusible link unit which can reliably suppress the temperature rise of the fuse circuit structures with little increasing of the external dimensions of the fuse circuit structures.
According to the present invention, there is provided a fusible link unit comprising:
a fuse circuit structure including a plurality of terminal parts linked through fusible members to a linking plate, and
a housing into which the fuse circuit structure is assembled,
wherein the fuse circuit structure is formed by laminating a plurality of part plates,
a first part plate includes a first linking portion constituting the linking plate by being laminted by a second linking portion of a second part plate, and
a respective part of the plurality of terminal parts which are connected to the linking plate with a respecitve part of the fusible members are provided with the first part plate.
In the fusible link unit thus constructed, current flowing through the linking plate of the fuse circuit structure branches into plural current paths to thereby suppress heat generation by the current flow.
In a preferred embodiment of the invention, the terminal parts with the fusible members connected thereto and the terminal parts, which are shared by the part plates, are substantially equal in number.
In the embodiment having the advantage mentioned above, current branches into the linking portions of the part plates at almost equal ratios.
In another embodiment, two part plates are used.
The fusible link unit of the embodiment has advantages comparable with those mentioned above.